docs: def glover_dispersion_derivative(tr, oversampling=50, time_length=32.,
                                   onset=0.):
      """Implementation of the Glover dispersion derivative hrf model
  
      Parameters
      ----------
      tr: float
          scan repeat time, in seconds
  
      oversampling: int, optional
          temporal oversampling factor in seconds
  
      time_length: float, optional
          hrf kernel length, in seconds
  
      onset : float, optional
          onset of the response in seconds
  
      Returns
      -------
      dhrf: array of shape(length / tr * oversampling), dtype=float
            dhrf sampling on the oversampled time grid
      """
      dd = .01
      dhrf = 1. / dd * (
          - _gamma_difference_hrf(
              tr, oversampling, time_length, onset,
              delay=6, undershoot=12., dispersion=.9 + dd, ratio=.35)
          + _gamma_difference_hrf(
              tr, oversampling, time_length, onset, delay=6, undershoot=12.,
              dispersion=.9, ratio=.35))
      return dhrf